Working on mine right now. I got a drum for free, I forget the height but it was supposed to be used for oil waste. It is Dept of Trans certified, which means it is thicker metal, has an extra rib for strength, and a hell of a lid. It was not used much at all, mostly sat in my step-dad's warehouse.
I burned it out twice, (man that thing is heavy as heck) and sanded it to bare metal. If I were to do another build, I'd pay to have it blasted clean. The money spent on sandpaper the time I put into it, and the filth caked all over me says blast it.
I have the holes drilled out for the intakes. I made them 7/8" and placed them every 18 inches. My drum measured out at 6' total diameter, so that's 4 intakes. I'm using the 3/4" pipe nipples with caps.
I am going to have my top grate 4" from the top, the second grate will be at 10". I drilled those holes and will use stainless screws and nuts and washers as the pins to hold the cooking grates.
I have two coats of paint on the drum so far. This drum will be two colors- green and gold. the ribs of the drum will be gold as will the lid. Flat parts are green. I want the smoker to work correctly so it'll be Green Bay Packer colors.
I think I'm going to use a sheet of rolled aluminum as the smoke stack.
I still have to build the charcoal basket, a heat shield (probably wait for that until after a few cooks) and tweak what ever needs doing.
I think I'll use a valve on one of the intakes for closing valve half way or less)
Lessons learned the hard way:
GET YOUR DRUM BLASTED. IT'S WORTH IT.
Do NOT rely on the "guy at Home Depot" to tell you all the right bits for yer pipe nipples. Rely instead on THIS HERE THREAD.
Do NOT sand the snot outta your drum and then wait two days to apply paint. Even though it's in the garage, the humidity will put some rust on there.
Perhaps most importantly-
This thread is a guide. Not spoken gospel. (ok maybe it actually is gospel) Do what YOU think is best for YOUR drum. All of us are doing the same general thing, but there are neat differences. My drum is not like yours. Yours is not like that dude's. His is not like mine.
If you don't want to spend a lot of time carefully taping out lines for your smoker, paint it all one color.
Taping took me a long time and I still loused it up I bet.
More to follow as I progress.
Oh- maybe the hardest lesson for me in this and in all things. BE PATIENT. Ya can't get ahead of yourself and expect not to make mistakes. I get all bent outta shape and want to see progress. I make dumb errors that way. GO S-L-O-W-L-Y.
UDS, Weber Performer, 18" Weber Silver, and a Smokey Joe. (I have a human-child too)